A device for a discontinuous fractionation of liquid density gradients yielding high resolution

When a liquid density gradient is fractionated through the bottom of a tube turbulences occur near the hole resulting in a mixing of closely spaced bands. To prevent this mixing the gradient is pumped upward and, in conventional instruments, guided through tubings into a fraction collector. Since mixing of bands in the tubings may occur, the advantage of pumping the gradient upward is diminished. To prevent this mixing an apparatus is described which, with the help of a peristaltic pump, collects fractions discontinuously after the gradient has been pumped upward thus preventing a mixing in instruments used for analysis and tubings attached to the fractionator.